The present invention relates to a method for manufacturing an electronic component that has a coil. Specifically, the electronic component may be a power supply module or a coil component, such as an inductor element.
In the field of electronic components, it is well known to manufacture a coil component having a dust core by a press machine. According to this method, the press machine presses a mixture of magnetic power and resin to seal a coil therewithin. This produces what is commonly referred to as a sealed coil-type magnetic component. Japanese Patent Publication Number JP 2007-81306 discloses a sealed coil-type magnetic component. The sealed coil-type magnetic component is configured with an air-core coil and a magnetic body. The magnetic body is made of a magnetic powder and resin mixture which seals the air-core coil. After the mixture is put in a metal mold of a press machine, the air-core coil is placed on the mixture. Thereafter, additional mixture is added over the air-core coil until the metal mold is filled. Next, upper and lower punches of the press machine press the mixture in the metal mold with a pressure of about 10 ton/cm2.
Unfortunately, because the sealed coil-type magnetic component is formed under high pressure, the air-core coil may be deformed or broken. As such, the manufacturing yield decreases.
In the field of electronic components, it is also well known to manufacture a power supply module by injecting a thermosetting or thermoplastic resin. Such a power supply module is often configured with passive components such as a coil, a resistor and a capacitor, and an IC that are assembled on a circuit board. Japanese Utility Model Publication Number JPU H05-38994 discloses a method of manufacturing one such power supply module. According to the disclosed method, after an electronic component is assembled on a metal board, thermoplastic resin is injected on and around the electronic component. Then, the thermoplastic resin is hardened. However, because the magnetic permeability of the thermoplastic resin is quite low, an electromagnetic wave generated at the electric component (i.e., the coil) is transferred to other areas inside the power supply device but outside the power supply module. Therefore, electromagnetic interference may occur.